During the second Mongol invasion, Tamerlane had met and very nearly annihilated another rising power: the Ottomans. Under a minor chieftain named Othman, groups of Turkish-speaking peoples in Anatolia were united in the Ottoman confederation which, by the second half of the fourteenth century, had conquered much of present-day Greece and Turkey and was threatening Constantinople.

The Ottoman state was born on the frontier between Islam and the Byzantine Empire. Turkish tribes, driven from their homeland in the steppes of Central Asia by the Mongols, had embraced Islam and settled in Anatolia on the battle lines of the Islamic world, where they formed the Ottoman confederation. They were called ghazis, warriors for the faith, and their highest ambition was to die in battle for their adopted religion.

In addition to their military abilities the Turks seem to have been endowed with a special talent for organization. Towards the end of the Ottoman Empire, this talent fossilized into bureaucracy - and a moribund bureaucracy at that. But at the beginning, when its institutions were responsive to the needs of the people and the state, the Ottoman Empire was a model of administrative efficiency. This, together with a series of brilliant sultans - culminating in the redoubtable Suleiman the Magnificent - established the foundations of an empire that at its height was comparable to that of the Romans.

The first important step in the establishment of this empire was taken in 1326 when the Ottoman leader Orhan captured the town of Bursa, south of the Sea of Marmara, and made it his capital.

It was probably during the reign of Orhan that the famous institution of the Janissaries, a word derived from the Turkish yeni cheri ("new troops"), was formed. An elite corps of slave soldiers conscripted from the subject population of the empire, they were carefully selected on the basis of physique and intelligence, educated, trained, introduced to Islam, and formed into one of the most formidable military corps ever known. At a later period the Janissaries became so powerful that they made and unmade sultans at their will, and membership in the corps was a sure road to advancement.

Photo: The mosque at Kyustendi in Bulgaria was founded during Ottoman rule.

Orhan's successor, Murad I, who launched naval attacks upon the Aegean coasts of Europe, established himself on the European shores of the Bosporus, and crushed a Balkan coalition. The next Ottoman leader was Bayazid I, who besieged Constantinople and routed the armies dispatched by an alarmed Europe to raise the siege.

It was at this point in history that Tamerlane and his Mongols advanced into Anatolia and very nearly crushed the Ottomans forever. They recovered, however, and later, under the leadership of a new sultan, Murad II, besieged Constantinople for the second time. They were repulsed, but by 1444 they had advanced into Greece and Albania, leaving Constantinople isolated though unconquered. Murad II was succeeded by Mehmed (Muhammad) II, called "The Conqueror" because on May 29, 1453, after his artillery finally breached Constantinople's massive walls, the city fell.

After the fall of Constantinople, and during the sixteenth century, the Ottoman system evolved the centralized administrative framework by which the sultans maintained effective control over the extraordinarily diverse peoples in the vast empire.

An important part of this framework was the millet system - essentially a division of the empire into a communal system based upon religious affiliation. Each millet was relatively autonomous, was ruled by its own religious leader, and retained its own laws and customs. The religious leader, in turn, was responsible to the sultan or his representatives for such details as the payment of taxes. There were also, however, organizations which united the diverse peoples. Particularly important were the guilds of artisans which often cut across the divisions of religion and location.

There was also a territorial organization of the empire, at the upper levels of which was a unit called the muqata'ah under the control of a noble or administrator who could keep some portion of the state revenues derived from it. The amount varied with the importance of the individual noble or administrator, and he could use it as he saw fit. Such rights were also given to some administrators or governors in place of, or in addition to, salaries, thus insuring a regular collection of revenues and reducing record keeping.

The Ottoman Empire reached its peak in size and splendor under the sultan called Suleiman the Magnificent, who ruled from 1520 to 1566 and was known to the Turks as Suleiman the Law-Giver. But from the middle of the sixteenth century on the empire began to decline. This process got under way as the office of the Grand Vizier gradually assumed more power and indifferent sultans began to neglect administration. Another factor was that the Janissaries became too strong for the sultans to control The sultans were further weakened when it became customary to bring them up and educate them in isolation and without the skills necessary to rule effectively.

Some sultans later regained power through political maneuvering and by playing off factions against one another, but as a result administration was paralyzed. When Europe found a new route to India - thus eliminating the traditional transshipment of goods through the Arab regions of the empire, revenues began to fall, triggering inflation, corruption, administrative inefficiency, and fragmentation of authority.

Temporary reforms under various sultans, and the still formidable, if weakened, military prowess of the Ottomans helped maintain their empire. As late as 1683, for example, they besieged Vienna. Nevertheless, the decline continued. Because of the increasingly disruptive part played by the Janissaries, the empire, in a series of eighteenth-century wars, slowly lost territory. Because of administrative paralysis, local governors became increasingly independent and, eventually, revolts broke out. Even the various reform movements were balked, and with the invasion of Egypt in 1798 by France it became obvious that the once powerful empire was weakening.

In 1824 Mahmud II finally broke the power of the Janissaries, brought in German advisers to restructure the army, and launched a modernization program. He also brought the semi-autonomous rulers in various provinces under control, with the exception of the defiant and able Muhammad 'Ali in Egypt. On the death of Mahmud, his sons continued his efforts with a series of reforms called the tanzimat. Some of these were no more than efforts to placate European powers - which by then had great influence on the empire's policies - but others, in education and law, were important. Again, however, the effects were temporary and the empire continued to lose territory through rebellion or foreign intervention.

By the early years of the twentieth century the Ottoman Empire was clearly in decline and was referred to as the "Sick Man of Europe." There were, however, some positive accomplishments in this period, such as the Hijaz Railway. Building the railway was undertaken in 1900 by Sultan Abdul-Hamid, as a pan-Islamic project. Completed in 1908, it permitted thousands of Muslims to make the pilgrimage in relative comfort and safety. It also helped to give the Ottoman government more effective control over its territories in western Arabia.

Photo: The Hijaz Railway, completed by the Turks in 1908, linked Damascus with Medina, eight hundred miles to the south.

During the early twentieth century too, a group called the Young Turks forced the restoration of the constitution (which had been suspended by Abdul-Hamid), eventually deposed the sultan, and again attempted to modernize the Ottoman state. The Turkish defeat in the First World War (in which the Ottoman Empire sided with Germany and the Central Powers) finally discredited the Young Turks, however, and paved the way for the success of a new nationalist movement under the leadership of an army officer named Mustafa Kemal, later known as Ataturk or "Father of the Turks." The nationalist government under Ataturk, dedicated to leading Turkey in the direction of secularism and Westernization, abolished the sultanate, declared a republic, and eventually (in 1924) abolished the caliphate as well.